1. Field of Invention
The present invention relates to a seal and, more particularly, to an electronic seal that includes several radio frequency identification units and a method based on an electronic seal for inspecting goods.
2. Related Prior Art
Referring to FIG. 1, there is shown a conventional electronic seal 900 for sealing a door of a container so that the door cannot be opened without cutting the electronic seal 900. The electronic seal 900 includes a plug 910, a socket 920, a radio frequency identification chip 930 and an antenna 940. The radio frequency identification chip 930 is located in the plug 910 while the antenna 940 is located in the socket 920. The radio frequency identification chip 930 is electrically connected to the antenna 940 as the plug 910 is inserted in the socket 920. An RFID reader is used to transmit reading waves to the radio frequency identification chip 930 through the antenna assembly 940 to excite the radio frequency identification chip 930 to transmit a specific code carried on the radio frequency identification chip 930. With the specific code, it can be determined whether the electronic seal 900 has been replaced. Thus, it can be determined whether the container has been replaced with another container or goods have been stolen from the container. There is an on-going trend to use the electronic seal 900 instead of a mechanical seal of which the integrity is generally checked by visually observing a number made on the mechanical seal or the outlook of the mechanical seal. Electronic seals are advantageous over mechanical seals where a lot of containers have to be checked in a short period of time.
In the customs all over the world, the radio frequency identification chip 930 of the electronic seal 900 is manufactured in compliance with the communication protocol and data format regulated in ISO 18000-6C/EPC, Class 1, Generation 2 which is made public. Hence, manufactures can develop their own devices to fulfill the requirements set by different customs. However, public standards make it easy for anybody to illegally read and record the specific code stored in the radio frequency identification chip 930 and then counterfeit another radio frequency identification chip similar to the radio frequency identification chip 930 and finally counterfeit another electronic seal similar to the electronic seal 900. In that case, the container could be opened after the electronic seal 900 is cut, and the container could be sealed again with the counterfeited seal instead of the electronic seal 900. It could be difficult, if not impossible, to find that the container has been opened and goods stolen from it or another container has been delivered instead of the container.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.